Batteries are used as a means for directly converting chemical energy to electrical energy. Batteries discharge electric charge, or repeatedly charge and discharge electric charge using electrochemical changes, and are therefore used as power sources of various electrical and electronic devices.
Recently, as secondary batteries with high energy efficiency, lithium ion batteries, lithium ion polymer batteries, etc., are used as power sources of mobile phones, personal computers, cameras, etc.
A positive electrode for lithium ion batteries is produced by applying a positive electrode active material slurry prepared by mixing a positive electrode active material (e.g., Li1+xMn2-x-yMyO4), carbon particles, a binder, and a solvent (e.g., N-methyl-2-pyrrolidone (NMP)) to an aluminum foil, which is used as a collector, then drying the slurry, and performing pressing to a predetermined thickness, as described, for example, in JP2003-68282A (hereinafter, PTL 1). Moreover, polyvinylidene fluoride (PVDF) having excellent chemical resistance, etc., is widely used as a binder, as described, for example, in PTL 1 and JP2000-507996A (PTL 2).